In general, shielding members such as curtains or blinds are used to hinder vision or shut out light through windows.
In order to adjust the room illumination by using such conventional shielding members, they had to be moved to the right/left or upper/lower direction, in which case the interior of a room could be seen from the outside and it could be an invasion of privacy or a public nuisance.
Thus, a new type of blind has recently been developed, wherein the blind comprises a blind sheet having alternate transparent and opaque parts and overlapped by folding, so that the room illumination can be adjusted without moving the blind to the right or left or to the upper or lower direction and without exposing the interior of the room to the outside.
FIG. 1 is a disassembled perspective view of such a conventional blind having an overlapping blind sheet, and FIG. 2 is a side view of a part of the blind wherein a clutch spring is provided in a bracket of the blind. FIG. 3 is a side view showing operating states of the conventional blind. Such conventional blind has been disclosed in Japanese Patent Laid-open Publication No. 1995-189,573.
A blind sheet (14) is folded to have a front blind sheet (14a) and a rear blind sheet (14b), with their upper end being wound or unwound together around a winding rod (12). The lower end of the blind sheet (14) is looped centering around a weight bar (16).
As shown in FIG. 3, the blind sheet (14) has alternate transparent and opaque parts (13 and 15) with a predetermined width.
The transparent parts (13) are formed by sparsely weaving the blind sheet (14), so that the air and light can penetrate into the room through it.
A clutch axis (18) is integrally formed with the winding rod (12) for rotation at the right end of the winding rod (12). The clutch axis (18) has a rectangular bore (20) in the center thereof, along its axial direction.
Further, a fluctuating rod (22) is provided between the front blind sheet (14a) and the rear blind sheet (14b) at a predetermined distance from the winding rod (12).
Both ends of the fluctuating rod (22) are respectively fitted to openings, which are respectively formed at ends of fluctuating members (23 and 24). At the other ends of the fluctuating members (23 and 24), openings (25 and 26) are provided to respectively fit to an end (12a) of the winding rod (12) and the clutch axis (18).
A protrusion (28) is formed below the opening (26) of the fluctuating member (24).
Also, a clutch spring (30) is provided adjacent to the fluctuating member (24) to be fitted to the periphery of the clutch axis (18).
The clutch spring (30) has both ends (30a and 30b) curved to the outside of the periphery of the clutch axis (18) so that the protrusion (28) formed below the opening (26) of the fluctuating member (24) can be positioned between the curved ends (30a and 30b).
When the blind sheet (14) is deployed to its farthest end, the clutch spring (30) is coupled to the clutch axis (18) to rotate integrally with the clutch axis (18). However, when a diameter of the clutch spring (30) increases by the movement of the fluctuating member (24) as described below, clutching of the clutch axis (18) is released, and then only the clutch axis (18) rotates.
Brackets (32 and 34) are provided beside the fluctuating members (23 and 24) at the ends of the winding rod (12a) and the clutch axis (18) to rotatably support the winding rod (12) and the clutch axis (18).
As shown in FIG. 1, a left bracket (32) has a receiving opening (33) into which the end of the winding rod (12a) passing through the opening (25) of the fluctuating member (23) is fitted. Also, a right bracket (34) has a receiving opening (36) into which the clutch spring (30) is fitted and also has a truncated part (38) in a lower part of the receiving opening (36).
The curved ends (30a and 30b) of the clutch spring (30) are located in the truncated part (38) and they move within the truncated part (38).
If one curved end (30a) of the clutch spring (30) is in contact with one end (38a) of the truncated part (38), the protrusion (28) of the fluctuating member (24) is vertically positioned, and if the fluctuating member (24) and the protrusion (28) are rotated to a predetermined angle, the other curved end (30b) of the clutch spring (30) comes into contact with the other end (38b) of the truncated part (38).
The clutch spring (30) is fitted to the clutch axis (18), which is therefore rotatably supported by the bracket (34).
Adjacent to the bracket (34), an operating gear (40) is provided, which has a rectangular bore (42) in the center thereof and is surrounded by using cord (44) along its periphery.
Into the rectangular bore (42) of the operating gear (40) and into the rectangular bore (20) of the clutch axis (18), a square bar (46) is inserted to integrally rotate the operating gear (40) and the clutch axis (18).
Accordingly, in order to lower the blind sheet (14), a string (44a) of the adjusting cord (44) is pulled down, so that the operating gear (40) rotates clockwise in FIG. 1.
Then, the clutch axis (18) and the winding rod (12) are rotated together with the operating gear (40) by the square bar (46), and the clutch spring (30) is also rotated clockwise in the receiving opening (36).
This rotation of the clutch spring (30) detaches the curved end (30a) of the clutch spring (30) from the end (38a) of the truncated part (38), and the rotation stops when the other curved end (30b) of the clutch spring (30) comes into contact with the other end (38b) of the truncated part (38).
During this rotation, the protrusion (28) is moved from the position A to the position B in FIG. 2 and the fluctuating rod (22) moves clockwise to the position B as shown in one-dot chain lines in FIG. 3.
Then, if the string (44a) of the adjusting cord (44) is further pulled down, the winding rod (12) will rotate further and the curved end (30b) of the clutch spring (30) will be pressed by the other end (38b) of the truncated part (38). As a result, the clutch spring (30) will become loose and be released from the clutch axis (18), so that only the winding rod (12) will keep rotating.
Accordingly, the blind sheet (14) can be pulled down to a desired position.
Then, if the blind sheet (14) is to be stopped, pulling down the adjusting cord (44) should be stopped, which will stop the rotation of the operating gear (40).
Accordingly, the winding rod (12) stops rotating and the blind sheet (14) is not pulled down any more.
When the operating gear (40) stops rotating, the clockwise rotational force from the clutch spring (30) does not act on the fluctuating member (24), but the downward force by the weight bar (16) acts on the fluctuating member (24), so that the fluctuating member (24) tends to rotate counterclockwise in FIG. 2.
Thus, the protrusion (28) of the fluctuating member (24) presses the curved end (30a) of the clutch spring (30) counterclockwise, and the clutch spring (30) is fastened to fit to the clutch axis (18). Therefore, the rotation of the fluctuating member (24) is restrained and the fluctuating rod (22) maintains the position B in FIG. 3.
When the fluctuating rod (22) is in the position B as in FIG. 3, the opaque parts (15) of the front blind sheet (14a) are overlapped with the transparent parts (13) of the rear blind sheet (14b) and the blind sheet (14) becomes entirely opaque, so that lighting and ventilation through the blind (10) cannot be done.
On the contrary, in order to light and ventilate through the blind (10), it is necessary to pull down the other string (44b) of the adjusting cord (44) to rotate the operating gear (40) counterclockwise.
Then, the clutch axis (18) and the winding rod (12) are rotated together with the operating gear (40) by the square bar (46) and the clutch spring (30) also rotates counterclockwise in the receiving opening (36).
If the clutch spring (30) rotates counterclockwise, the other curved end (30b) of the clutch spring (30) is detached from the other end (38b) of the truncated part (38), and the rotation continues until the curved end (30a) of the clutch spring (30) comes into contact with the end (38a) of the truncated part (38).
During this rotation, the protrusion (28) is moved from the position B to the position A and the fluctuating rod (22) moves counterclockwise to the position A as in FIG. 3.
Therefore, by overlapping the transparent parts (13) or the opaque parts (15) of the front blind sheet (14a) with those of the rear blind sheet (14b) by the rotation of the fluctuating member (24), the blind sheet (14) can adjust lighting and ventilation.
However, the conventional blind (10) as described above had the following disadvantages.
Firstly, since the conventional blind necessitated a pair of fluctuating members (24), the fluctuating rod (22) and the clutch spring (30) to align the transparent parts (13) or the opaque parts (15) of the front and rear blind sheets or to alternate them, it was not economical in terms of manufacturing costs and the productivity.
Secondly, even if the blind sheet (14) were to be unwound by pulling down the adjusting cord (44), it happened occasionally that the front blind sheet (14a) was suspended or held on the winding rod (12) and the blind sheet (14) could not be unwound smoothly.
Thirdly, since the front blind sheet (14a) was kept slant by the fluctuating rod (22), while the rear blind sheet (14b) was kept vertically, it was difficult to adjust the transparent and opaque parts to be exactly overlapped.
That is, since the front blind sheet (14a) was positioned distant from the rear blind sheet (14b), it was not easy to adjust illumination appropriately.
Finally, since the front blind sheet (14a) was to be positioned away from the rear blind sheet (14b) by the fluctuation of the fluctuating rod (22), a lot of space around windows was required for installation of the conventional blind.